Printheads for inkjet printers are precisely manufactured so that the components cooperate with an integral ink reservoir to achieve a desired print quality. Despite the precision, the printheads containing the ink reservoir are disposed of when the ink supply in the reservoir is exhausted. Accordingly, the components of the assembly need to be relatively inexpensive so that the total per page printing cost, into which the life of the assembly is factored, can be kept competitive in the marketplace with other forms of printing.
Typically the ink, and the materials used to fabricate the reservoir and the printhead, are not the greatest portion of the cost of manufacturing the printhead assembly. Rather, it is the labor intensive steps of fabricating the printhead components themselves. Thus, efforts which lower the cost of producing the printhead have the greatest effect on the per page printing cost of the inkjet printer in which the printhead assembly is used.
One method for lowering the cost for production of printheads is to use manufacturing techniques which are highly automated. This saves the expense of paying highly skilled technicians to manually perform each of the manufacturing steps. Another method for reducing production costs is to improve the overall yield of the automated manufacturing process. Using a higher percentage of the printheads produced reduces the price per printhead thus spreading out the cost of manufacture over a greater number of saleable pieces. Since process yields tend to increase as the number of process steps required to manufacture a part decrease, it is desirable to reduce the number of process steps required to manufacture the printhead, or replace complex, low yield process steps with simpler, higher yield process steps.
Inkjet printheads are often formed from two or three major components including, 1) a substrate containing resistance elements to energize a component in the ink, and 2) an integrated flow features/nozzle layer to direct the motion of the energized ink. The flow features of the printhead may be contained in the nozzle layer or in a separate layer attached to the nozzle layer or substrate. The individual features which must cooperate during the printing step are contained in the components, which are joined together before use. Typically, an adhesive is used to join the components of the printhead into a unitary structure.
If the adhesive is applied to one of the components before the manufacturing steps for that component are completed, then the adhesive layer may retain debris created during subsequent manufacturing steps. Often the debris is difficult to remove, and at the very least requires extra processing steps to remove, thus increasing the cost of the printhead. Additionally, if the debris is not completely removed the adhesive bond between the substrate and the nozzle layer may be impaired, resulting in a printhead which either functions improperly, or does not exhibit the expected utility lifetime. Therefore, the yield reduction caused by unremoved debris increases the cost of producing the printheads.
If the adhesive is applied to one of the components after the features are formed in that component, additional labor intensive steps are required to ensure that the adhesive is positioned on the portions of the component that are to be used as bonding surfaces, and that the adhesive is removed from those portions of the component whose function will be inhibited by the presence of the adhesive. Not only do these extra steps add to the cost of the printhead, but any error in positioning the adhesive on the components will tend to reduce the yield of product from the printhead manufacturing process.
For example, if adhesive is left in a portion of the component such as a flow channel for the ink, then the proper function of that flow channel will be inhibited, and the printhead will be unusable. Alternately, if the adhesive does not adequately cover the bonding surfaces between the components, then the components may separate, allowing ink to leak from the completed assembly. Both of these conditions will lower the product yield, thereby increasing the cost of the printheads produced, as explained above.
It is an object of this invention, therefore, to provide a method for manufacturing an inkjet printhead that is highly automated.
It is another object of this invention to provide an inkjet manufacturing method that does not require additional process steps for the alignment and removal of adhesive.
It is a further object of this invention to provide a method for manufacturing an inkjet printhead in which the adhesive used to join the components does not attract and retain debris through subsequent process steps.